Achieving the Widest Range of Syngas Proportions at High Current Density over Cadmium Sulfoselenide Nanorods in CO₂ Electroreduction

Electroreduction of CO₂ is a sustainable approach to produce syngas with controllable ratios, which are required as specific reactants for the optimization of different industrial processes. However, it is challenging to achieve tunable syngas production with a wide ratio of CO/H₂ , while maintaining a high current density. Herein, cadmium sulfoselenide (CdS_x Se_1-x ) alloyed nanorods are developed, which enable the widest range of syngas proportions ever reported at the current density above 10 mA cm^-2 in CO₂ electroreduction. Among CdS_x Se_1-x nanorods, CdS nanorods exhibit the highest Faradaic efficiency (FE) of 81% for CO production with a current density of 27.1 mA cm^-2 at -1.2 V vs. reversible hydrogen electrode. With the increase of Se content in CdS_x Se_1-x nanorods, the FE for H₂ production increases. At -1.2 V vs. RHE, the ratios of CO/H₂ in products vary from 4:1 to 1:4 on CdS_x Se_1-x nanorods (x from 1 to 0). Notably, all proportions of syngas are achieved with current density higher than ≈25 mA cm^-2 . Mechanistic study reveals that the increased Se content in CdS_x Se_1-x nanorods strengthens the binding of H atoms, resulting in the increased coverage of H* and thus the enhanced selectivity for H₂ production in CO₂ electroreduction.